FISHERY BULLETIN: VOL. 74, NO. 1 



cell size and the ability to take up nutrients 

 (Dugdale 1967; Eppley et al. 1969; Eppley and 

 Thomas 1969). Large species generally have 

 higher half saturation constants (Kg) and may 

 have higher maximum uptake rates (Vmax)' 

 whereas small species have low^er Kg and V^ax 

 (Dugdale 1967). Maximum net plankton grovi'th 

 rates are favored at higher ambient nutrient 

 concentrations while nannoplankton reach their 

 maximum growth rates at lower ambient nutrient 

 levels. There is also a direct relationship of in- 

 creasing cell size (or chain length) with increas- 

 ing sinking rates (Smayda 1970), and larger cells 

 and chain formers tend to be aggregated in 

 areas of upward advection, while motile or posi- 

 tively buoyant cells tend to be concentrated in 

 areas of downward advection (Stommel 1949). 

 Net plankton will have a longer residence time 

 in the euphotic zone and concentrate in areas 

 of upwelling, while the nannoplankton (if the 

 population is primarily motile flagellates) will be 

 concentrated in areas of downwelling. 



Parsons and Takahashi (1973) related the 

 growth rate (/u,) to physiological characteristics of 

 the cell (maximum grovvi:h rate, half saturation 

 constants for nutrients and light, and sinking 

 rates) and environmental conditions (incident 

 radiation, extinction coefficients, mixed layer 

 depth, and upwelling rates) and used the rela- 

 tionship to explain characteristic phytoplankton 

 cell size in a number of environments. Recently, 

 Laws (1975) expanded the Parsons and Taka- 

 hashi model and showed that under certain light 

 conditions the decreasing respiration rate with 

 increasing cell size may regulate the growth rate 

 of large versus small cells. 



The effect of grazing on the net:nanno ratios 

 and, conversely, the size of the primary producers 

 on food chains have not been well documented. 

 Grazing may ultimately control net plankton 

 stocks (Malone 1971c; Ryther et al. 1971) and de- 

 termine the lower net:nanno standing stock ra- 

 tios in oceanic as opposed to neritic areas (Malone 

 1971a). Grazing has been suggested as the pri- 

 mary cause for failure of phytoplankton stocks 

 to develop in otherwise favorable waters (Mc 

 Allister et al. 1960; Strickland et al. 1969). 

 Shorter food chains have been shown for some 

 clupeid fishes which feed directly on the large 

 phytoplankton species (e.g., Bayliff 1963; Rojas 

 de Mendiola 1969; Dhulkhed 1972) and for her- 

 bivorous euphausids in the diatom-rich antarctic 

 region (Marr 1962). The general argument for 



larger phytoplankton cells resulting in shorter, 

 more efficient food chains may not always apply 

 to the smaller grazers, as Parsons and LeBras- 

 seur (1970) have reported on selective feeding re- 

 lated to cell shape. 



Previous studies have been made on the hydro- 

 graphic seasons in Monterey Bay and their rela- 

 tionship to the seasonal phytoplankton blooms 

 (Bolin and Abbott 1963; Abbott and Albee 1967). 

 Malone (1971c) reported the seasonal variability 

 of the net plankton and nannoplankton in the 

 California Current, which included one deep sta- 

 tion on the edge of Monterey Bay. The present 

 study was part of a monthly sampling program 

 conducted by Moss Landing Marine Laboratories 

 to provide information on the hydrographic con- 

 ditions and plankton populations in Monterey 

 Bay, particularly from the extensive shallow 

 areas of the bay. Although it was not possible to 

 carry this study through a complete seasonal cy- 

 cle, information is presented for the upwelling 

 period, when seasonal blooms of phytoplankton 

 appear in Monterey Bay. 



MATERIALS AND METHODS 



Measurements of primary productivity and 

 phytoplankton standing stocks were made at sta- 

 tions 3 and 8 for the period January through Au- 

 gust 1972 and at station 15 for the period June 

 through August 1972 (Figure 1). The stations 

 were located over the Monterey Submarine Can- 

 yon at depths of 110, 240, and 718 m, respectively. 

 Samples were taken monthly during hydrograph- 

 ic and plankton cruises conducted by Moss Land- 

 ing Marine Laboratories and, occasionally, be- 

 tween these periods on instructional cruises. 

 Sampling times varied between cruises but fell 

 between 0700 and 1100 h. 



Samples were collected with 5-liter Niskin 

 water sampling bottles from depths correspond- 

 ing to 100, 50, 25, 10, and 1% light penetration 

 levels as measured with a submarine photometer 

 or calculated using the relationship: depth of 1% 

 light = 3.5 X Secchi disk (Silver and Hansen 

 1971a). Hydrographic parameters (salinity, °L; 

 temperature, °C; O2) and nutrients (PO4, NO3, 

 NO2, NH3, Si02) were samples at standard depths 

 (Broenkow and Benz 1973). 



Primary productivity was measured using the 

 carbon-14 method (Steeman Nielsen 1952). For 

 each depth two light and one dark bottles were 

 innoculated with 5 or 10 fxCi of Naa^^COg. The 



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